Theoretical studies of the distribution of ionic charge in polynucleotide solutions will be carried out. The first objective of this research is the development of a detailed description, at the molecular level, of the spatial distribution of simple salt ions around an extended polynucleotide chain and an analysis of the dependence of this distribution on small ion size and charge, as well as polyelectrolyte charge density. Corresponding studies with simple salt mixtures will be carried out in order to develop a correspondingly detailed picture of competitive ionic association. Such studies will provide a much more detailed picture of the ionic environment of polynucleotides than is presently available from experimental structural studies, such as those using NMR techniques. Further, the results will provide tests of the reliability of less detailed, but also more readily evaluated, theoretical descriptions such as those following from the Poisson-Boltzmann equation or the condensation theory developed by Manning. The studies will employ state-of-the-art statistical mechanical methods, including integral equation and computer simulation techniques; each of these is a proven approach to the study of simple electrolyte solutions. The primary polynucleotide model will be that of a uniformly charged rod; this model has been shown in earlier work to be very valuable for the interpretation of experimental data. Logical refinements of the model to include a more realistic polyelectrolyte charge distribution, polymer flexibility, and an accurate treatment of solvent effects will be examined. The results will elucidate fundamental aspects of the molecular solution structure which underlie polynucleotide conformation and polynucleotide interactions with nucleic acids and polypeptides. Important examples include the role of the ionic environment in the formation of the compact polynucleotide structures occurring in cellular chromatin and in viral environments, and in the formation of nucleic acid-ribosome complexes. The research will provide the necessary basis for longer-term studies aimed at a quantitative molecular description of these complex processes.